The old OP_RESCUE took one operand A, which specifies a class
to match with the exception. The new OP_RESCUE takes tree operands:
A: the register to hold exception
B: the matching exception; the match result will be stored here.
C: the continuation; if C is zero, the exception will be stored to R(A)
otherwise, the value from R(A) is used as a exception.
Thus,
```ruby
begin
raise "a"
rescue TypeError
p 1
rescue RuntimeError
p 2
end
```
will be compiled as
```
irep 0x557a06667aa0 nregs=4 nlocals=1 pools=1 syms=4 reps=0
file: /tmp/e.rb
2 000 OP_ONERR 005
2 001 OP_LOADSELF R1
2 002 OP_STRING R2 L(0) ; "a"
2 003 OP_SEND R1 :raise 1
2 004 OP_JMP 022
3 005 OP_GETCONST R2 :TypeError
3 006 OP_RESCUE R1 R2
3 007 OP_JMPIF R2 009
3 008 OP_JMP 013
4 009 OP_LOADSELF R1
4 010 OP_LOADI R2 1
4 011 OP_SEND R1 :p 1
4 012 OP_JMP 023
5 013 OP_GETCONST R2 :RuntimeError
5 014 OP_RESCUE R1 R2 cont
5 015 OP_JMPIF R2 017
5 016 OP_JMP 021
6 017 OP_LOADSELF R1
6 018 OP_LOADI R2 2
6 019 OP_SEND R1 :p 1
6 020 OP_JMP 023
6 021 OP_RAISE R1
6 022 OP_POPERR 1
6 023 OP_STOP
```
The new VM can accept old OP_RESCUE. The mruby compatible VM (namely
mruby/c) should be updated to support the new OP_RESCUE behavior.
There are 3 levels of C++ exception handling:
* default - no C++ exception (use setjmp/longjmp)
* enable_cxx_exception (use C++ exceptions with C ABI)
* enable_cxx_abi (use C++ ABI including exceptions)
CRuby defines #instance_exec in BasicObject, but we don't.
It's a small incompatibility that isn't worth accomplish at
the price of implementation complexity.
- String#ljust and String#rjust are now C functions to improve performance
- infinite loop because of an empty padding argument is now prevented (ArgumentError is raised)
- extra tests for ljust/rjust added
The new API is:
int mrb_range_beg_len(mrb, range, &beg, &len, len, trunc)
The new argument `trunc` is a boolean value that specifies
whether the function truncates the range. The new return value
is an integer instead of a boolean, that is:
0: not a range
1: range with proper edges
2: out of range
To get the old behavior, you have to rewrite:
mrb_range_beg_len(mrb, range, &beg, &len, len)
to:
mrn_range_beg_len(mrb, range, &beg, &len, len, TRUE) == 1
[Breaking Change]
ksss